Field
Exemplary embodiments relate to a touch screen panel. More particularly, exemplary embodiments relate to a touch screen panel including a capacitive type touch sensor.
Discussion of the Background
Display devices, such as a liquid crystal display (LCD), an organic light emitting diode (OLED) display, and an electrophoretic display, include a field generating electrode and an electro-optical active layer. For example, the OLED display includes an organic emission layer as the electro-optical active layer. The field generating electrode is connected to a switching element, such as a thin film transistor, to receive a data signal, and the electro-optical active layer converts the data signal to an optical signal to display an image.
Recently, such a display device may include a touch sensing function in which interaction with a user can be performed, in addition to a function of displaying the image. The touch sensing function determines touch information, such as whether an object approaches or touches a screen, a touch position thereof, and the like, by sensing changes in pressure, charges, light, and the like, which are applied onto the screen by the display device whenever a user writes a text or draws a figure by approaching or touching the screen with a finger or a touch pen. The display device may receive an image signal based on the touch information to display an image.
The touch sensing function may be implemented by a touch sensor. The touch sensor may be classified into various types, such as a resistive type, a capacitive type, an electro-magnetic (EM) type, and an optical type.
In the case of the resistive type touch sensor, two electrodes that are spaced apart from each other while facing each other may contact each other by pressure due to an external object. When two electrodes contact each other, a change in voltage according to a resistance change at a touch position is recognized, and thus, the touch position and the like may be determined.
The capacitive type touch sensor includes a sensing capacitor configured by a sensing electrode which may transfer the sensing signal, and may determine whether there is a touch, a touch position, and the like by sensing a change in capacitance of the sensing capacitor generated when a conductor, such as a finger, approaches the sensor. The capacitive type touch sensor may sense the touch only when a user touches a touch screen and requires a touch by a conductive object.
The touch screen may be included in a flexible electronic device that has been recently developed. However, as a result of the flexible characteristic of the flexible electronic device, it has been determined that an electrode of the touch screen should also have flexibility so as to prevent a defect from being generated.
The flexible material of the electrode may include, for example, various materials, such as a metal nano wire, such as silver nano wire (AgNW), a carbon nanotube, graphene, a metal mesh, or a conductive polymer.
Because such materials have low conductivity, in order to compensate for conductivity on a pad of the touch screen, a separate pad is required as a low resistive metal, such as copper.
However, when an external signal is applied to the pad and the pad is exposed, the pad is easily oxidized to produce corrosion that may be dispersed over the entire touch sensor. As a result, the reliability of the screen may be markedly reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.